THEY’RE just machines aren’t they? One hundred and two tons of metal forged and hammered into shape to fulfil a function.

Mallard at The Great Goodbye

Well yes, and no. If that’s all they were we wouldn’t care about them would we?

Not only do we care, we are in awe of these machines. This morning I involuntarily smiled when I heard one of them whistle, a sound carried on the breeze across the north of Darlington, as it made its way down the branch line from Shildon.

And we cared in huge numbers over the last week or so as the remaining six Class A4 Pacific steam locomotives went on show at Locomotion in Shildon (http://www.nrm.org.uk/PlanaVisit/VisitShildon) in an event named The Great Goodbye.

I was one of 18,000 to visit on Saturday. Organisers expected 72,000 visitors over the nine days, they eventually welcomed 120,000. Shildon, not a big place, came to a standstill at times, overwhelmed by traffic. Normally empty two-car trains heading for the event were leaving Darlington full-and-standing.

The A4s were built between 1935 and 1938. Much of the love for them relates to the world speed record set by the most famous of these six survivors – Mallard – as it hurtled down a bank north of Peterborough at 126mph in 1938. It is little remembered that Mallard then broke down, and never completed the run into Kings Cross.

It helps that the A4s are streamlined. Their curves speak of speed. They were nicknamed Streaks. Like the Spitfire, or Concorde, or the Tyne Bridge, they are beautiful. What they all share is that their designers and builders managed to combine engineering and purpose with grace.

Union of South Africa steams along a short line at Locomotion, Shildon

One of the guides at the event pointed out that the A4s remained in service into the 1960s. After their glamour days were over they finished their working days painted black, pulling goods trains. The last ran in 1966.

It was Sir Nigel Gresley, named after the man who designed the A4s, I heard this morning. Union of South Africa and Mallard left yesterday. Bittern will take its leave tomorrow. Dwight D Eisenhower and Dominion of Canada will be at Shildon for a few weeks yet, before going back to their homes across the Atlantic.

I’m glad to have had the chance to see the six together. And I’m glad that someone saw beyond the metal and the functional to save them.